It is already known that it is possible to digitize handwriting by determining how a pen used to create the handwriting is moved. One way of doing this is to use a base for the handwriting provided with a position-coding pattern which codes coordinates for points on the base, and also to provide the pen with a sensor which records the position-coding pattern locally at the tip of the pen as the pen is moved across the base. A processing unit, which can be placed in the pen or at a distance therefrom, can then decode the recorded position-coding pattern so that the movement of the pen across the base can be determined as a series of coordinates.
WO 01/26032, which is assigned to the applicant of the present application, describes a position-coding pattern which can be used precisely for digitizing handwriting. The pattern is made up of marks, which for example can be in the form of dots. Each dot has a nominal position represented by an intersection between two lines in a virtual raster, for example a square grid. Each dot codes a fixed value depending on its location in relation to the nominal position. The dots can have four possible locations, for example, one on each of the four raster lines extending from the intersection, the four different locations coding four different values. The coordinates of a point are coded with the aid of a plurality of dots, for example 6*6 dots. However, each dot contributes to the coding of the coordinates of a plurality of points. If a sensor first reads 6×6 dots and is thereafter moved one dot distance to the side or vertically, the sensor will read dots which code the coordinates of a new point. This type of pattern in which the position resolution is smaller than the size of the partial surface required for determining a position is in the present application referred to as “floating”.
Using the position-coding pattern in the above-mentioned WO 01/26032, coordinates for a very large number of points can be coded, theoretically 436 points if each point is coded with 6*6 dots. All these points can be said to form an imaginary surface or form dots in a coordinate system.
WO 01/48685, which is also assigned to the applicant of the present invention, describes how such an imaginary surface can be used for information management. More specifically, different partial areas on the imaginary surface are dedicated to different types of information management. It is then possible to control how information which is recorded digitally is to be handled by providing bases with a position-coding pattern which corresponds to different partial areas on the imaginary surface. For example, a first base can be provided with a position-coding pattern which means that information which is written on the position-coding pattern and is recorded digitally by the pen is sent to a predetermined computer for storage in the latter. Correspondingly, another base can be provided with a position-coding pattern which means that information which is recorded digitally with the aid of this position-coding pattern is sent as an e-mail to an address indicated by the user on the base.
WO 01/48685 also describes how the pen which records the position-coding pattern can store different digital templates, which define how the information from different parts of physical bases with position-coding patterns is to be interpreted. An e-mail template can, for example, specify that a base with a corresponding position-coding pattern has a first field which is intended for a message, a second field which is intended for an e mail address to be interpreted by ICR (Intelligent Character Recognition), and a third field which constitutes a send box which the user ticks in order to initiate the sending of a recorded message.
Different bases can have fields with different functions. The number of fields can be different on different bases. The fields can further be located in different places on the bases, which besides may be of different sizes.
As is also described in WO 01/48685, the position-coding pattern can be arranged differently on the physical base. According to a first alternative, the position-coding pattern on the base can be continuous, which means that it corresponds to a continuous area of the imaginary surface. The processing unit which is to interpret and process the digital information recorded from the base must then know the layout of the base, i.e. which fields there are on the base and where these are located. If many different layouts are allowed, which is of course desirable, many different digital templates must be stored so as to be accessible to the processing unit. This is particularly a problem if the processing unit has a limited storage capacity and/or if it takes a long time to change the information once it has in fact been stored. This may be the case, for example, if the processing unit is arranged in a portable user unit, such as the pen in WO 01/48685.
According to a second alternative, the position-coding pattern on the base can correspond to a combination of a plurality of separate partial areas on the imaginary surface so that the position-coding pattern on the base will be discontinuous. In the above example the first field can then correspond to, for instance, a first partial area on the imaginary surface which is dedicated to message information, the position-coding pattern in the second field can correspond to a second partial area which is dedicated to address information which is to be processed by ICR, and the position-coding pattern in the third field can correspond to a third partial area which is dedicated to send boxes. In this case, the location of the fields on the base is thus not related to the location of corresponding partial areas on the imaginary surface. In this alternative, the unit which is to interpret and process the digital information from the base has to store a smaller quantity of information because it only needs to know the coordinates of the different partial areas on the imaginary surface.
In certain situations, however, a continuous position-coding pattern on the base is still to be preferred. If the pattern is of the floating type, positions will not be able to be defined in a boundary area between two different fields in the discontinuous position-coding pattern since the dots in the boundary area do not code coordinates for adjacent points on the imaginary surface. One way of solving this problem is to have no position-coding pattern in the boundary area so that points belonging to one or the other field can be detected unambiguously. Such boundary areas without position-coding pattern can be undesirable, especially when the product is small.
A further problem with a discontinuous position-coding pattern on the base may arise if the sensor in the pen is displaced from a pen point of the pen used to make graphical notes on the physical base. It may then happen that the pen point is placed in a first field in the discontinuous position-coding pattern, but that the sensor, owing to the displacement, records the position-coding pattern in another field on the base, which in turn may result in the pen not performing the function intended by the user.
The position-coding pattern corresponding to a digital template can be applied as it is on a base. Alternatively, different partial areas of the position-coding pattern corresponding to the digital template can be “cut out” and arranged in a different spatial arrangement on the base. The different partial areas of the digital templates correspond to different fields, which may have different functions, on the base.
The pen does not need to know the spatial arrangement of the different fields on the base in order to determine how to handle coordinates recorded from the base. However, if the movement of the pen over the base is to be displayed by an external unit, e.g. a PC, to which the coordinates are sent, the PC needs to know the spatial arrangement of the fields on the base. Unfortunately, the PC cannot determine the spatial arrangement from the coordinates sent to it from the pen.